Re: [PATCH] fb: sh-mobile: Fix deadlock risk between lock_fb_info() and console_lock()

Florian Tobias Schandinat
2011-09-02T20:54:51Z

On 09/02/2011 05:24 PM, Bruno Prémont wrote:
> Following on Herton's patch "fb: avoid possible deadlock caused by
> fb_set_suspend" which moves lock_fb_info() out of fb_set_suspend()
> to its callers, correct sh-mobile's locking around call to
> fb_set_suspend() and the same sort of deaklocks with console_lock()
> due to order of taking the lock.
>
> console_lock() must be taken while fb_info is already locked and fb_info
> must be locked while calling fb_set_suspend().
>
> Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> ---
>
> Hi Florian,
>
>> On the other hand I just noticed the original patch didn't have
>> Bruno's Signed-off and a commit message was missing. So may I ask you,
>> Bruno, to add your Signed-off or preferably resend the version tested
>> by Guennadi in the appropriate patch format.
>
> Here it is with commit message and the Signed-off-by's.

Applied and added stable as Cc as I think this should be applied as well
whenever Herton's patch is applied.

Thanks,

Florian Tobias Schandinat

>
> Thanks,
> Bruno
>
>
>
>
> drivers/video/sh_mobile_hdmi.c | 47 ++++++++++++++++++++++-----------------
> 1 files changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/video/sh_mobile_hdmi.c b/drivers/video/sh_mobile_hdmi.c
> index 7d54e2c..647ba98 100644
> --- a/drivers/video/sh_mobile_hdmi.c
> +++ b/drivers/video/sh_mobile_hdmi.c
> @@ -1111,6 +1111,7 @@ static long sh_hdmi_clk_configure(struct sh_hdmi *hdmi, unsigned long hdmi_rate,
> static void sh_hdmi_edid_work_fn(struct work_struct *work)
> {
> struct sh_hdmi *hdmi = container_of(work, struct sh_hdmi, edid_work.work);
> + struct fb_info *info;
> struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
> struct sh_mobile_lcdc_chan *ch;
> int ret;
> @@ -1123,8 +1124,9 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)
>
> mutex_lock(&hdmi->mutex);
>
> + info = hdmi->info;
> +
> if (hdmi->hp_state == HDMI_HOTPLUG_CONNECTED) {
> - struct fb_info *info = hdmi->info;
> unsigned long parent_rate = 0, hdmi_rate;
>
> ret = sh_hdmi_read_edid(hdmi, &hdmi_rate, &parent_rate);
> @@ -1148,42 +1150,45 @@ static void sh_hdmi_edid_work_fn(struct work_struct *work)
>
> ch = info->par;
>
> - console_lock();
> + if (lock_fb_info(info)) {
> + console_lock();
>
> - /* HDMI plug in */
> - if (!sh_hdmi_must_reconfigure(hdmi) &&
> - info->state == FBINFO_STATE_RUNNING) {
> - /*
> - * First activation with the default monitor - just turn
> - * on, if we run a resume here, the logo disappears
> - */
> - if (lock_fb_info(info)) {
> + /* HDMI plug in */
> + if (!sh_hdmi_must_reconfigure(hdmi) &&
> + info->state == FBINFO_STATE_RUNNING) {
> + /*
> + * First activation with the default monitor - just turn
> + * on, if we run a resume here, the logo disappears
> + */
> info->var.width = hdmi->var.width;
> info->var.height = hdmi->var.height;
> sh_hdmi_display_on(hdmi, info);
> - unlock_fb_info(info);
> + } else {
> + /* New monitor or have to wake up */
> + fb_set_suspend(info, 0);
> }
> - } else {
> - /* New monitor or have to wake up */
> - fb_set_suspend(info, 0);
> - }
>
> - console_unlock();
> + console_unlock();
> + unlock_fb_info(info);
> + }
> } else {
> ret = 0;
> - if (!hdmi->info)
> + if (!info)
> goto out;
>
> hdmi->monspec.modedb_len = 0;
> fb_destroy_modedb(hdmi->monspec.modedb);
> hdmi->monspec.modedb = NULL;
>
> - console_lock();
> + if (lock_fb_info(info)) {
> + console_lock();
>
> - /* HDMI disconnect */
> - fb_set_suspend(hdmi->info, 1);
> + /* HDMI disconnect */
> + fb_set_suspend(info, 1);
>
> - console_unlock();
> + console_unlock();
> + unlock_fb_info(info);
> + }
> }
>
> out:
>